Marathoning Hard on the Heart

Endurance athletes' hearts often show reduced function in one area after a workout. But less exercise isn't the answer.

We tend to think the more exercise you do, the better. But as serious athletes will tell you, prolonged exercise can be hard on the body. The joints and muscles can often take a beating. New research shows that the heart – the very organ that should benefit from exercise the most – can also be adversely affected, at least temporarily.

'It is most important that our findings are not over-extrapolated to infer that endurance exercise is unhealthy,' said La Gerche. 'Our data do not support this premise.'

In the new study, researchers looked at the hearts of endurance athletes: marathon runners, endurance triathletes, alpine cyclists, and ultra triathletes. Their heart tissue was analyzed before their respective competitions, an hour afterwards, and six to 11 days after.

Right after their competitions, the participants’ hearts had increased in size, and the right ventricle had decreased in function. The right ventricle pushes oxygen-depleted blood out of the heart so it can be re-oxygenated in the lungs. No participants showed damage to the left ventricle, which receives and pumps oxygen-rich blood to the body.

ADVERTISEMENT

Six to 11 days later, the damage had reversed in 35 of the 40 athletes. But the other five athletes continued to show fibrosis, or scar tissue, around the right ventricle. Interestingly, the researchers noted that the five participants who showed this continued damage were also the most seasoned athletes of the group.

The results will surely spark many future studies to look into the link between high levels of activity and heart health. "Large, prospective, multi-center trials are required to elucidate whether extreme exercise may promote arrhythmias in some athletes,” said author Andre La Gerche. “To draw an analogy, some tennis players develop tennis elbow. This does not mean that tennis is bad for you; rather it identifies an area of susceptibility on which to focus treatment and preventative measures.”

What should not be seen as the take-home message is the idea that vigorous exercise leads to more damage than benefit. "It is most important that our findings are not over-extrapolated to infer that endurance exercise is unhealthy," said La Gerche. "Our data do not support this premise." Of course, athletes and regular folk who exercise should always be careful to do it safely. As with many things in life, moderation is usually the best bet, since overdoing anything can lead to health problems.

The study was carried out by researchers at the University of Melbourne and University Hospitals Leuven in Belgium, and published in the European Heart Journal.